In the large, non-stick skillet, melt the butter in the oil. When hot, add the leeks and cook over moderate heat until softened, about 3 minutes. Add the garlic and cook, stirring occasionally, until softened, about 5 minutes. Add the spinach and cook, stirring, until the spinach is incorporated with the leeks and garlic. Add the heavy cream and Pernod and cook over high heat, stirring, until the cream has thickened, about 1 minute. Season with salt and pepper and let cool to room temperature.